Method and apparatus for reducing particle size



June 19, 1962 M. I. COHN ETAL METHOD AND APPARATUS FOR REDUCING PARTICLE SIZE Filed Dec. 24, 1958 2 Sheets-Sheet 1 INVENTORS COHN PERDUE mm mm ATTORN EYS June 19, 1962 M. I. COHN ETAL 3,039,703

METHOD AND APPARATUS FOR REDUCING PARTICLE SIZE Filed Dec. 24, 1958 2 Sheets-Sheet 2 FIG. 2

LINQNQNNV mm A v 7 INVENTORS MORRIS l. COHN QOY D. PERDUE 081%, Maxim ATTOR N EYS United States Patent Ofifice 3,039,703 Patented June 19, 1962 3,039,703 METHOD AND APPARATUS FOR REDUCING PARTICLE SIZE Moms I. Cohn, Needham, and Roy D. Perdue, Tewksbury, Mass., asslgnors to Mineral Industries Corporation of America, Boston, Mass., a corporation of Massachusetts Filed Dec. 24, 1958, Bar. No. 782,816 21 Claims. (Cl. 241-5) The present invention relates to a method of and apparatus for grinding and delaminating mica and other minerals, especially mica derived from mica schist ores.

In copending application Serial No. 758,930, filed September 4, 1958, now abandoned, and of which this application is a continuation-in-part, there is described a method and apparatus for grinding and delaminating mica and other minerals. The method comprises applying a high fluid pressure on a liquid slurry of mica particles in the form of books or blocks of laminated layers of mica to force it to flow at a high velocity through a highly restricted opening formed by closely spaced hard surfaces. The slurry is discharged from the opening at a high velocity against a hard impact surface directly in front of the opening. Shearing, turbulence, shattering, impact and cavitation forces are imparted to the mica particles or books as they flow into and through the opening and against the impact surface to delaminate and grind them into fine flakes. In a preferred embodiment, the restricted opening comprises a valve opening and the slurry under high pressure is directed against the valve to force it slightly away from its seat against the force of resilient means such as a spring or the like yieldingly urging it toward its seat, whereby the slurry under pressure is forced or squirted at an extremely high velocity through the highly restricted opening between the valve and its seat and against the impact surface. The direction of flow of the slurry through the valve opening is at an angle (in most cases about 90) to the direction of flow to and against the valve. The valve opening is preferably annular in shape and extends in a radially outward direction whereby the slurry flows therethrough in a radially outward direction. The fluid pressure is generated by a pressure pump such as a piston pump operating on the slurry and the impact surface comprises an impact ring extending around the annular valve opening. The

valve seat is in the form of a hollow cylinder, an end face of which forms an annular valve seat surface. The slurry feed under pre sure flows through the bore of the cylinder against the valve located over the end face of the valve seat. The valve is a solid cylinder and the end thereof forms a solid circular valve face which cooperates with the annular valve seat surface to form the annular valve opening.

It has been found that the abrasive action of the mica as it is pumped in lurry form through the valve assembly described in the above mentioned application causes a radially extending channel to be worn in the annular valve seat surface and a ring shaped groove to be worn in the circular face of the valve where the slurry changes its direction of flow and is accelerated in rate of flow as it is directed into and enters the restricted valve opening.

The ring shaped groove in the valve face destroys or alters the working surface of the valve face and thereby prevents the achievement of a proper uniform clearance between the valve face and the valve seat surface. As a result the quality and uniformity of the resulting delaminated mica deteriorates.

The mica slurry tends to channel through the channel in the valve seat surface, thereby reducing velocity and shear effects on the mica particles and making pressure control and the achievement of proper slurry velocities difiicult or impossible. This prevents proper delamination and consequently causes the quality and uniformity of the resulting delaminated mica to deteriorate.

To remedy this, it is necessary to periodically remove the valve and valve seat from the valve assembly and lap and polish the valve face and the valve seat surface by conventional machine shop practice. This is time consuming and makes it necessary for the equipment to be idle during a good deal of the time unless spare parts are retained.

It has been found that the formation of the radially extending channel in the valve seat surface can be substantially eliminated and that the ring shaped channel on the valve face is formed more uniformly by rotating the solid valve. A valve assembly in which the valve is so rotated is described in application Serial No. 782,992, which is also a continuation-in-part of application Serial No. 8,- 930, which describes and shows in detail the way in which the channel and groove are formed and which is being filed concurrently herewith. The rotation of the valve causes the layer of slurry between the valve surface and valve seat surface to lap such surfaces and consequently wear them uniformly, whereby the formation of a channel is prevented. However, the formation of the ring shaped groove in the valve face where the slurry enters the restricted valve opening is not eliminated by rotating the valve and consequently it is still necessary to periodically remove the valve and valve seat and relap and polish the valve face and valve seat surface.

It is an object of the present invention to provide a method and valve assembly of the above mentioned type in which the formation of the ring shaped groove in the valve face as well as the channel in the valve seat surface are substantially eliminated.

It is another object of the present invention to substantially extend the useful life of a valve assembly of the type described above before removal and regrinding or relapping of the valve face and the valve seat surface become necessary.

It is another object to minimize or eliminate altogether the above-mentioned difficulties caused by wear to thereby reduce the cost of manufacture and improve the uniformity of the product.

-It is another object to eliminate the necessity of periodically removing the valve and valve seat and relapping and polishing the valve face and the valve seat surface.

It is yet another object to provide an improved method and apparatus for reducing particle size and more specifically for delaminating and/or grinding mica and other minerals.

These objects are accomplished by providing a recess or cavity in the face of the valve, the mouth of such recess having a cross-sectional area which is at least as large and preferably the same as the crosssectional area of the end of the bore of the valve seat in the end face of such seat, whereby a cup-shaped valve is provided. The mouth of the recess has substantially the same crosssectional shape as the end of the bore and the recess is ardally aligned with the bore so that the mouth of the recess faces the end of the bore.

Preferably, the cup-shaped valve is in the form of a hollow cylinder having the same internal and external diameters as the cylindrical shaped valve seat and axially aligned therewith.

The cup-shaped valve is rotated about its longitudinal center axis.

In a preferred embodiment, the cylindrical shaped valve seat is simultaneously rotated about its longitudinal center axis in a direction opposite from the direction in which the valve is rotated.

Improved results are obtained by also simultaneously rotating the impact surface or ring about its center axis J and by providing a blade shaped member, which is rotated within the bore of the valve seat and with respect to the valve seat.

Preferably, the blade shaped member is anchored to the floor of the recess in the valve and extends axially through the recess and 'a substantial distance into the bore of the valve seat. Consequently, the blade shaped member is located in the flow path of the slurry through the bore of the valve seat and acts as an agitator to agitate the slurry.

The invention will be more clearly understood from the following description in conjunction with the accompanying drawings in which:

FIG. 1 is a view in elevation and partially in section of an embodiment of the improved valve assembly of the present invention with the slurry tank in which the slurry is formed and the pump for pumping the slurry against the valve being shown diagrammatically.

FIG. 2 is an enlarged view of the valve assembly of the present invention showing the valve, the valve seat, the impact ring, the blade shaped member and the fluid chamber into which the slurry is discharged from the valve opening.

' FIG.'3 is a view taken along the line 33 of FIG. 2.

FIG. 4 is a view taken along the line 44 of FIG. 2.

Before explaining in detail the present invention, it is to be understood that it is not limited in its application to the details and arrangements illustrated and descirbed herein, since it is capable of other embodiments and of being practiced or carried out in various ways. Also, the terminology employed and the theories described herein are for the purposes of description and explanation and not of limitation and it is not intended to limit the invention claimed herein beyond the requirements of the prior With reference to the drawings, the mica ore (schist, pegmatite, alaskite or other mica deposits) is first crushed into small particles in a conventional ore crushing mechanism (not shown), garnet and heavy minerals, if present, are then removed from the crushed ore and silica and other non-micaceous minerals are then removed from the mica in a conventional froth flotation unit (not shown) or other mica concentrator utilizing water and suitable flotation agents if necessary.

The mica and water discharged from the flotation unit flow through line 2 (FIG. 1) to the mica slurry feed tank 4 to which additional water is added through line 3 to obtain the desired concentration of mica in water. The mica and water are agitated in tank 4 by agitator 5, to produce a uniform mica slurry feed which is fed by gravity or a pump through line 6 to the inlet 7 of liquid piston pump 10. The slurry is sucked from inlet 7 through suction ball check valve 13 into the pump cylinder 14 by the suction stroke of piston 16 and is forced under 7 pressure through discharge ball check valve 18 and pump outlet 20 into and through the bore 22 of a rotating shaft 24 and thence into and through the bore 26 of a cylindrical shaped valve seat28 to the rotating cylindrical shaped, hollow valve 30. Valve seat 28 is attached to and rotates with shaft 24. The force exerted by the high pressure slurry on the cylindrical shaped valve 34) in a right hand direction as viewed in FIG. 1 forces the end face 31 of-the valve slightly away (a fraction of an inch) from the end face 32 of itsvalve seat 28 against the force of a coil spring 33 urging the end face 31 of valve 39 toward the end face 32 of the valve seat through the thrust bearing assembly 34 and rotating shaft 36 with which the valve rotates, Whereby'the slurry under pressure flows atan extremely high velocity through the highly restricted valve opening 38 between the opposed end faces 32 and 31 of the rotating valve seat 28 and rotating valve '30 respectively against an annular-impact ring 40 extending'around and spaced from the peripheries of the adjacent end portions of the valve 30 and valve seat 28. The slurry then flows through the narrowpassage 41 between the ring 40' and the peripheries of the adjacent end portions of the valve and seat into the low pressure fluid chamber 43 from whence it flows through the outlet 44 to either another pressure pump and valve assembly (not shown) or .toa screen or other type of classifier (not shown)-where the coarser mica particles are separated and, if desired, are recycled back to the water slurry'feed tank, as 'shown and described in original application Serial No. 758,930. Theparticles of suflicient fineness and degree ofdelamination are flowed from the screen or classifier to a centrifuge or thickener (not shown) where excess water is removed. The centrifuged particles are then dried and deagglomerated and the finished delarninated and ground mica passing from the deagglomerator is ready for bagging.

Delamination and grinding are achieved by the following: shearing eifect on'the mica particles by the closely spaced valve seat surface 32 and the valve face surface 31 forming the restricted opening 38 and by the closely spaced impact ring 40 and outer peripheries of the valve 30 and valve seat 28 forming passage41, all of which are made of a very hard material such as tungsten carbide; turbulence and cavitation of the mica particles as they flow into and through the opening'38 against impact ring 40 and into and through passage 41; and shattering and impact of the particles against the impact ring 40. The vmious changes in the direction of flow of the slurry from the bore 26 of the valve seat 28 to the restricted opening 38 and from the restricted opening 38 to the passage 41 also contribute to the delamination and grinding phenomena. It is also believed that the liquid media contributes to the effect of these delaminating and grinding forces.

The end of the hollow, cylindrical shaped valve 30 opposite from its working end face 31 is fixed in an end of rotating shaft 36 by a press fit or the like of the end of the cylinder in a recess in the end of the shaft. The end of the bore 35 of the hollow valve 30 opposite from the end in face 31 is closed by the floor 37. of the recess in the shaft 36, as shown.

Considering the floor 37 of the recess in the shaft 36 as part of the valve 39, the valve'30 may be described as being cup-shaped in that it is open at the end facing the valve seat and is closed at its opposite end.

The bore 35 may be considered as a recess or cavity in the face 31 of the valve 30, the floor 37 being the floor of such recess or cavity in the valve face and the wall of the bore 35 comprising the side wall of'the recess or cavity.

Referring to 'FIG. 2, the inside diameter g (diameter of bore or cavity 35) and the outside diameter b of the valve cylinder 3!} are substantially the same as the inside diameter a (diameter of bore 26) and outside diameter h respectively of the valve seat' cylinder 28. Consequently, considering bore 35 'of the valve as a recess or cavity in the working face 31 of the valve; the crosssectional area of such cavity or recess at the face 31 of the valve 30' is substantially the same as the cross-sectional-area-of the passage or bore 26 in the valve seat 28 at its working face 32 and has substantially the same contour or shape. The bore or cavity 35 and its longitudinal center axis are axially aligned with the bore 26 and its longitudinal center axis respectively.

The cross-sectional area of. bore 35 at the valve face 31 can be greater than the cross-sectional area of bore 26 at the valve seat face 32 but should-not be substantially smaller. Although it is preferred that the outside diameters of the valve 30 and valve seat 28 be substantially the same so that the passage 41 on either side of the valve opening 38 is uniform, .thisis not essential. 'It is also not essential that the cross-sectional contour of the cavity 35, valve 30, bore 26 and valve seat 28' be round or that they be the same. However, it is desirable to avoid having any substantial portion .of the solid part of face 31 extending radially inwardly beyond the wall of bore 26 in order to avoid wearing of the valve face.

Cup-shaped valve 30 and shaft 36 rotate as a unit, the shaft 36 and hence valve 30 being rotatably supported by two radial bearing assemblies 41a and 42 and entering the end wall 43a of the fluid chamber 43 through a stuffing box 44a. The radial bearings 41a and 42 are press fitted into radial bearing supports 45 and 46 respectively and the stufiing box 44a prevents leakage of water and mineral particles along the outside of shaft 36 from the fluid chamber 43 by means of several rings of packing 47, a packing follower 48 and a packing compression nut 49.

Rotational motion is imparted to the shaft 36 by means of a pulley 50 which is keyed to the shaft 36. The pulley 50 is driven by a motor 51, pulley 52 and V-belt 53.

As stated above, the annular working end face 31 of the cylindrical valve 30 is urged axially to the left as shown in FIG. 1 toward the cooperating annular valve seat surface 32 of the cylindrical shaped valve seat 28 by compression spring 33 acting on the end of the shaft 36 through a thrust bearing assembly 34. Thrust bearing assembly 34 permits the shaft 36 to rotate while being urged to the left by the stationary spring 33.

Thrust bearing assembly 34 comprises a plate 34a which is urged to the left as viewed in FIG. 1 by coil spring 33. Plate 34a acts on plate 3412 through ball bearings 34c and through the engagement of plate 34a with hub 34d of plate 345 to urge plate 34b to the left. Plate 34b acts on the end of shaft 36 to urge it axially to the left through ball bearings 34c and plate 34 afiixed to the end of the shaft. Ball bearings 34e permit the shaft 36 and valve 30 to rotate while at the same time urging the shaft and valve axially to the left. The plates and ball bearings are housed within a free floating housing 34g which is anchored against rotation but is free to move longitudinally. Plate 34b can be integral with the housing. Any conventional thrust bearing assembly can be used.

The amount of force exerted on valve 30 by the spring 33 can be adjusted by means of a compression adjustment plug 62 to thereby vary the slurry pressure required to force the valve 30 open and the size at of the restricted opening 38 at any particular slurry pressure. The plug 62 is threaded in a supporting wall 63 and has a hollow passage in which is loosely fitted the spring rod 64. Rod 64 also fits loosely in an aperture in plate 34a.

Turning the plug 62 in one direction so that it moves axially to the left, as shown in FIG. 1, compresses the spring 33 and increases the spring force exerted on the valve 30. Turning the plug 62 in the other direction so that it moves axially to the right decreases the spring forces exerted on the valve 30. Continued axial movement to the right of plug 62 is finally transferred through nut 65 and spring rod 64 to plate 34b in which the spring rod is threaded to move the plate 34b to the right and thereby release the spring force on the valve 39 so the unit can be disassembled.

In addition to providing for the rotation of the cup shaped valve 30, the valve seat 28 can also be rotated countercurrently to, or in a direction opposite to the rotation of, the cup shaped valve 30. Rotational movement is imparted to the valve seat 28 by the hollow rotating shaft 24 to an end of which the cylindrical valve seat 28 is afiixed by means of a press fit of an end of the valve seat cylinder 28 in a recess in the end of shaft 24, with the bores 22 and 26 of the hollow shaft 24 and valve seat cylinder 28 respectively in axial alignment. The diameters of the two bores 22 and 26 may be equal but this is not essential.

Hollow shaft 24 is rotatably supported on two radial bearing assemblies 76 and 77 held in two bearing supports or holders 78 and 79 respectively. The shaft 24 is rotated by pulley 80 which is keyed to shaft 24 and is driven by a second motor 81, pulley 82 and V-belt 83.

Hollow shaft 24 differs from shaft 36 in that the former is hollow and allows for the mineral slurry to be pumped under pressure from pump 1%) through the bore 22 of the shaft and bore 26 of the valve seat 28 to the cup shaped valve 38.

A liquid seal is provided at the end of the shaft 24 by a stufling box 85, packing 86, packing follower 87 and packing compression nut 88. The stufiing box 85 is supported by and extends through the supporting wall 89. An end of shaft 24 extends into and rotates within an enlarged end portion of passage 85:: extending through stufling box 85. The packing 86 is located Within said enlarged end portion and around the end of the shaft 24 to provide the liquid seal. The bore 22 of shaft 24 is axially aligned with and of the same diameter as the narrow end portion of passage 85a. The slurry is pumped through the narrow end portion of passage 85a into the bore 22 of the hollow shaft 24.

The rotating shaft 24 enters the end wall 94 of the liquid chamber 43 through a stuffing box 9% fitted with packing 91, packing follower 92 and a packing compression nut 93.

A thrust bearing assembly 84 counters the force imposed on the valve seat 28 and the shaft 24 by the spring 33 through valve 30 while at the same time permitting rotation of the shaft 24. Thrust bearing assembly 84 comprises a hollow member or housing 84a fixed in an aperture in a supporting wall 84b with the shaft 24 extending through the bore of member or housing 84:: as shown. The bore of member 84a is enlarged at 340. The shaft has a flange 84a alhxed thereto or integral therewith and located within the enlarged portion 34c of the bore in 84a. The force exerted on the valve seat 28 and shaft 24 by the spring 33 acting through the shaft 36 and valve 3% is countered by the flange 84e acting on stationary shoulder 84 of member 84a through the ball bearings 84g. Put in another way, shoulder 84 acts through ball bearings 84g and flange 84:2 to prevent movement of shaft 24 and valve seat 28 to the left. Ball bearings 84h are located between the rotating flange 84a and stationary retaining plate 84d which retains the ball bearing assemblies within the bore of member 84a and which, through ball bearings 84]: and flange 842, prevents the shaft 24 from moving axially to the right. The ball bearings 84g and 84h permit the shaft 24 and hence the valve seat 28 to rotate while at the same time preventing the shaft and seat from moving to the left to thereby counter the force exerted on the valve seat and shaft 24 by the spring 33.

The impact ring 40 can be stationary and supported on a supporting wall which in turn is supported on the cylindrical shaped wall 69 of the fluid chamber 43, as described in the above mentioned continuation-in-part application of Serial No. 758,930 filed concurrently herewith, or it can be mounted in a cylindrical bracket 98 by a press fit as shown in FIG. 1. The bracket 98 is threaded onto or otherwise attached to the end of shaft 36 as shown so that the impact ring 40 rotates with and at the same speed as the shaft 36 and valve 30 and consequently in the same direction as the valve but in a direction opposite from the direction of rotation of the valve seat. However, the impact ring 40 can be rotated with the valve seat 28 instead of the valve or can be rotated independently of the valve and valve seat. Holes 99 and are drilled in the bracket 93 to permit the slurry to escape from the right hand side of the impact ring 40. Under all conditions, especially when feeding a slurry with coarse particles, smoother and quieter operation of the valve assembly results with the use of a rotating impact ring.

A valve assembly having a rotating cup-shaped valve and a counter rotating valve seat is referred to herein as a counter-rotating valve assembly. With such an arrangement and under the proper conditions described in application Serial No. 758,930, fine delaminated mic-a can be continuously produced While minimizing or eliminating deleterious wear effects on the valve assembly parts by the abrasive mica slurry.

The process as described herein and in patent application Serial No. 758,930 is useful for making coarser grinds of mica such as those in demand by the roofing industry. In making such coarser grinds the feed particles pumped to the valve in slurry form are generally coarser than the feed used in making joint cement and paint grade mica. With a valve which does not rotate, as described in application Serial No. 758,930, or with a rotating valve 30 and/ or a rotating valve seat and/or a rotating impact ring, as herein described, these coarser particles in flowing through restricted opening 38 force the valve back and temporarily widen the restricted opening 38. When the large particle has passed through the opening, the spring 33 instantly urges the valve back to its former position, but there is an over-travel of the valve so that the closely spaced surfaces 31 and 32 strike and a hammering sound results. The valve and valve seat may become chipped from this hammering.

It has been found that this hammering can be elimininated by a blade one circular end of which is threaded into the floor 37 of the recess in the end of rotating shaft 36, which floor forms the floor of the recess or cavity 35 in the face of valve 3% and the bottom of the rotating cup shaped valve 39, as shown in FIG. 1. The threads are arranged so as to tighten when the valve is rotated. The blade extends into a fiat blade portion %a. The blade extends axially through the bore 35 of the valve 3% and a substantial distance into the bore 26 of the valve seat 28 and is coaxial with the bores 35. and 26, both of which are axially aligned, as shown. The shaft 36. rotates the blade 96 within the bore 26 of valve seat 28 in a direction opposite to the direction of rotation of the valve seat. The blade rotates with the valve 39 and with respect to the valve seat 28. Width K (see FIGS. 3 and 4) of the blade 96a should be as large as possible consistent with free rotation within the bore 26 of valve seat 28, which bore has an inside diameter a. The effects which the rotating blade has in eliminating the hammering eifect are not fully understood, but are nevertheless apparent. The blade apparently beats or agitates the slurry and breaks up agglomerates.

Vlhen feeding slurries with coarse particles to the rotating valve not only is the hammering effect eliminated with the use of such a blade but also higher pressures can be achieved while still retaining smooth operation.

Blade 96 can be used whether or not the valve and/ or valve seat and/or impact ring are rotated.

The blade 96 may extend entirely through the valve seat 28into the bore 22 of the rotating shaft 24 and can be rotated independently of the valve or be stationaryif the valve seat is rotated.

The hollow cup-shaped valve 30 has an advantage over the solid form of the valve disclosed in original patent j application Serial No. 758,930 by eliminating the formation of the ring shaped groove in the face of the valve and hence eliminating the necessity of periodically removing the valve and lapping the valve face.

'Solid mica particles 35a (FIG. '2) are deposited and accumulate in the cavity or recess '35 (bore in the valve cylinder) in the valve face. Although the exact phenomena whichactually occur within the cavity 35 during operation of the apparatus is not certain, when the unit is disassembled the cavity is tightly packed with solid begins to form at and slightly radially inwardly of the circular line on the valve -face opposite the circular edge of the inner wall of the cylindrical valve seat and gradually widens in a radially outward direction so that eventually it i located in the portion of the valve face opposite the valve seat surface of the valve seat and interferes with the maintenance of proper and uniform clearances between the two opposed surfaces.

Either the surface 74 of the packed mica in FIGS. 1 and 2 resists the formation of such a groove or the surface is continuously regenerated so that the groove cannot spread to the working portion 31 of the valve face opposite the valve seat surface 32.

Although the slurry is actually directed against the surface 74 of the mass of tightly packed mica particles accumulated in the cavity 35, it is considered as being directed against the valve 30 in the sense that it forces the valve to the right against the force exerted on the valve by the spring 33 to thereby, open the valve and cause the slurry to move at high velocity through the highly restricted valve opening from the high pressure area 26 to the lower pressure area (substantially atmospheric) in the fluid chamber 43.

By rotating the cup shaped valve and/ or the valve seat, a radially extending channel is not worn into the valve seat surface 32 and consequently the necessity of periodically removing the valve seat and relapping surface 32 is eliminated.

If desired the corners 1G1 and 102 (FIG. 2) of the valve and valve seat respectively may be slightly bevelled to prevent them from being worn or cracked ofi by the abrasive action of the slurry.

The parts of the valve subject, to the most severe conditions, i.e., the cup shaped valve 3?), the valve seat 28 and the impact ring 48, are preferably made of the hardest obtainable material such as tungsten carbide. Because of the high cost, of these materials, the apparatus in FIG. 1 has been designed so that these parts are of minimum size and can be replaced if necessary.

The rotating action of the valve 30 with respect to the valve seat 28 causes the slurry between the valve seat face '32 and valve face 31 to impart a constant lapping and polishing action on such faces, which prevents the formation of radially extending channels in the face 32 of the valve seat. This lapping or grinding action causes the valve face 31 and valve seat face 32 to wear uniformly.

Since the spring 33 continues to urgethe valve toward the valve seat, uniform Wearing of the surfaces 32 and 31 does not do any substantial harm and the equipment can be operated for very long periods of time without overhaul.

The above mentioned lapping action on the surfaces 31 and 32 is achieved not only by rotation of the valve with the valve seat remaining stationary but also by rotation of the valve seat with the valve remaining stationary and it is increased by the rotation of-both in opposite directions. 7 t

The rotation of the impact ring 40 with respect to the valve seat 28 prevents plugging of the passage 41 by the mica particles especially when coarse feeds are used.

The use of blade-shaped member '96 rotating within the bore 26 and with respect to the valve seat 28 prevents plugging of the restricted opening 38 probably because it breaks up mica agglomerates.

The shafts 36 and 24 can each be rotated as slowly as 0.5 revolution per minute (r.p.m.) or less and as fast as 3450 r.p.m. or more. Conventional motor speeds such as 1750 r.p.m. can be used. However, about 600-800 r.p.m. is the preferred range and about 400 r.p.m. has been found to give excellent results These speeds can be achieved through proper selection of'the motor 51 and the pulleys 5t} and 52 in the case of shaft 36 and through the proper selection of motor 81 and the pulleys 8t and 82 in the case of shaft24. The two shafts may 9 be rotated at the same or different speeds. When rotated at different speeds, the rotation of each may be in the same direction but this is not preferred.

The rotational motion imparted to the valve and/or valve seat and/or impact ring may be reciprocating.

Flow through the valve assembly of FIG. 1 should be adequate to provide a film or layer of slurry between the surfaces 31 and 32, which layer of slurry provides a lapping action on the surfaces and prevents them from rubbing against each other. For example, with a valve seat having a dimension a of 0.250 inch a flow of approximately four gallons per minute (g.p.m.) or more is adequate.

The fluid chamber 43 is formed by a curved cylindrical wall 69 or a series of flat walls such as a box and is closed at the ends by the plates 94 and 43a.

The fluid chamber 43 and the supporting walls 63, 84b and 89 and the bearing supports 45, 46, 78 and 79 are all supported on a frame (not shown) extending along the length of the valve assembly.

Although in FIG. 1, the valve, valve seat and impact ring are all rotated, the formation of a ring shaped groove in the face of the valve is prevented by providing the valve face with cavity 35 even without rotation of any of these parts. Furthermore, good results are obtained if the cup-shaped valve is rotated and the valve seat and impact ring are not. Also the valve and valve seat may be rotated without rotation of the impact ring or the valve seat can be rotated without rotation of the valve or impact ring or with rotation of either one of them, or the impact ring can be rotated without rotation of the valve or valve seat or with rotation of either one of them.

Although the use of blade 96 gives better results with a coarse feed, good results are obtained without it. The use of blade 96 also gives better results with substantially all feeds and may be used with or without rotation of the valve and/ or the valve seat and/ or the impact ring.

The dimensions a (diameter of bore 26), b (outside diameter of valve 3%)), (distance between the impact ring and outer peripheries of the valve seat and valve), d (distance between surfaces 31 and 32 or size of the restricted valve opening 38), e (width of impact ring) and f (thickness of the wall of the valve seat cylinder 28) are substantially the same as the corresponding dimensions in the valve assembly described in application Serial No. 758,930. However, the invention is not limited to such dimensions and they may vary considerably depending upon the capacity of the unit.

The preferred ranges of the dimensions d and c are the same as those described in the above mentioned original application Serial No. 758,930. Also (1) the mica concentrations of the slurry feed, (2) the particle size range of the mica particles in the slurry feed or average particle size of the particles in the feed, (3) slurry pressures, (4) slurry velocities through valve opening 38, (5) rates of slurry feed to the pump and valve assembly, and (6) the spring forces are substantially the same as those described in original application Serial No. 758,930 and can be varied over the ranges specified in such application. Thus, the lower limit of slurry pressure is 100 pounds per sq. inch whereas more practical pressures are from about 500 and 600 pounds per sq. inch to 6,000 pounds per sq. inch and more. As a matter of fact, except under exceptional conditions 250 pounds per square inch may be considered as a lower limit and 500 pounds per square inch as a practical lower limit.

Furthermore, the slurry feed may be passed through the same or different pump and valve assemblies a number of times and coarse particles in the slurry emerging from the valve assembly may be recycled to the slurry tank as described in the original application.

The effect of varying the above mentioned variables is the same as in the original application.

The procedures set forth in the examples in the original application produce the same results described in such application when carried out with the apparatus of FIG. 1 but with such apparatus, no ring shaped groove is worn in the valve face and no radially extending channel is worn in the valve seat surface and consequently the valve and valve seat do not have to be periodically removed to relap and polish the valve face and valve seat surface. Furthermore, with the use of blade 96, coarse particles do not cause hammering and efficiency is substantially increased.

The method and apparatus described herein can be used beneficially to grind any kind of mineral, especially minerals that occur in the form of laminated layers like mica, such as talc. Furthermore, they can be used to reduce the particle size of particles other than minerals, and to disperse particles in a liquid or other particle carrying media. The terms liquid slurry of particles and particles in the form of a liquid slurry, as used herein, include any flowable mixture of the particles in a liquid.

We claim:

1. An apparatus for reducing the size of particles comprising a portion having an internal passage through which a liquid slurry of said particles under pressure is adapted to flow, an end of said passage being in a face of said first portion, a second portion having a face facing said face of said first portion, said face of said second portion having a cavity facing and axially aligned with said end of said passage, said cavity having a cavity floor, said faces being adapted to be spaced closely to each other to form a highly restricted opening therebetween extending at an angle to the longitudinal center axis of said passage and having a width which is substantially smaller than the width of said passage, means for delivering a liquid slurry of said particles to said passage and restricted opening under a high pressure of at least pounds per square inch to force the slurry through said restricted opening at an angle to the direction of flow thereof through said passage and at a high increased velocity, said cavity containing a bed of particles against which said slurry under pressure is directed.

2. An apparatus for reducing the size of particles comprising a valve seat having an internal passage, a face of said valve seat comprising a valve seat surface, an end of said passage being in said face of said valve seat, a valve having a valve face facing said face of said valve seat, said valve face having a cavity therein facing said end of said passage and yieldable means for urging said valve face toward said valve seat surface, means for delivering to said passage and valve said particles in the form of a liquid slurry under pressure, said valve face being adapted to be forced away from said valve seat surface by the pressure exerted on said valve by said slurry and against the force exerted by said yieldable means to provide a highly restricted valve opening between said valve face and said valve seat surface through which said particles are forced at a high velocity substantially greater than the velocity through said passage, said opening extending in a direction at an angle to the direction of flow of said slurry to said valve, the width of said valve opening being substantially smaller than the width of said passage, said cavity containing a bed of particles against which said slurry under pressure is directed.

3. An apparatus according to claim 2 including means for imparting rotational motion to said valve face, said rotational motion being about an axis which is coaxially disposed with respect to the longitudinal axis of said passage.

4. An apparatus according to claim 2, including means for imparting rotational motion to said valve seat face.

5. An apparatus for reducing the size of particles comprising a valve seat having an internal passage, a face of said valve seat comprising a valve seat surface, an end of said passage being in said face of said valve seat,

avalvev having a valve face facing said face of said valve seat, said valve face having a cavity therein facing said end of said passage, yieldable means for urging said valve face toward said valve seat surface, means for delivering to said passage and valve said particles in the form of a liquid slurry under pressure, said valve face being adapted to be forced away from said valve seat surface by the pressure exerted on said valve by said slurry and against the force exerted by said yieldable means to provide a highly restricted valve opening between said valve face and said valve seat surface through which said particles are forced at a high velocity substantially greater than the velocity through said passage, said opening extending in a direction at an angle to the direction of flow of said slurry to said valve, the Width of said valve opening being substantially smaller than the width of said passage, said apparatus including a blade-shaped member located in said passage in said valve seat and means for providing relative rotational motion between said valve seat and said. member.

6. An apparatus for reducing the size of particles comprising a valve seat having an internal passage, a face of said valve seat comprising a valve seat surface, an end of said passage being in said face of said valve seat, a valve having a valve face facing said face of said valveseat, said valve face having a cavity therein facing said end of said passage, yieldable means for urging said valve face toward said valve seat surface, means for delivering to said passage and valve said particles in the form of a liquid slurry under pressure, said valve face being adapted to be forced away from said valve seat surface by the pressure exerted on said valve by said slurry and against the force exerted by said yieldable means to provide a highly restricted valve opening between said valve face and said valve seat surface through which said particles are forced at a high velocity substantially greater than the velocity through said passage, said opening extending in'a direction at an angle to the direction of flow of said slurry to said valve, the width of said valve opening being substantially smaller than the width of said passage, said apparatus including a blade member located in said passage-of said valve seat and means for imparting rotational movement to said valve face, said bladesshaped member being attached to the floor of said cavity and extending axially through said cavity into said passage of said valve seat, said blade-shaped member being rotated with said valve face.

7. An apparatus according to claim 2, including an impact member having an impact surface spaced from and facingthe peripheral edges of said valve and valve seat faces.

8. An apparatus according to claim 7,' including means for imparting rotational motion to said impact surface.

9. .An apparatus for reducing the size of particles comprising a valve seat having an internal passage, a face of said valve seat comprising a valve seat surface, an end of-said passage being in said face of said valve seat, a valve having a valve face facing said face of said valve seat, means for imparting rotational movement to said valve'seat surface during operation of the apparatus, yieldable means urging said valve face toward said valve seat surface and means for delivering said particles in the form of liquid slurry under a high pressure of at least 100 pounds per square inch to said passage and said valve to force said valve face away from said valve seat surfaceand thereby provide a highly restricted opening between said valve face and valve seat surface which is substantially smaller in width than said passage and through which said slurry is forced at a high velocity substantially greater than the velocity through said passage, said passage having a blade member located therein and means for imparting rotational movement to said blade member in a direction opposite tothe direction of rotation ofsaid valve seat.

10. An apparatus for reducing the size of particles comprising a valve seat having an internal passage, a face of said valve seat comprising a valve seat surface, an end of said passage being'in said face of said valve seat, a valve having a valve face facing said face of said valve seat, means for imparting rotational movement to said valve seat surface during operation of said apparatus, yieldable means urging said valve face toward said valve seat surface and means for delivering said particles in the form of liquid slurry under a high pressure of at least pounds per square inch to said passage and said valve to force said valve face away from said valve seat surface and thereby provide a highly restricted opening between said valve face and valve seat surface which is substantially smaller in width than said passage and through which said slurry is forced at a high velocity substantially greater than the velocity through said passage, said apparatus including an impact member having an impact surface facing and spaced from the peripheral edges of said valve face and said valve seat surface, said impact surface extending at an angle to said faces.

11. An apparatus according to claim 10, including means for imparting rotational movement to said impact surface in a direction opposite to the direction of rotation of said valve seat during operation of said apparatus.

12. An apparatus for reducing the size of particles comprising a valve seat having an internal passage, a face of said valve seat member comprising a valve seat surface, an end of said passage being invsaid face of said valve seat, a valve having a valve face facing said face of said valve seat, an impact member having an impact surface facing and spaced from thetperipheral edges of said valve face and said valve seat face and extending at an angle to said faces, means for imparting rotational movement to said impact surface during operation ofsaid apparatus.

13. An apparatus for reducing the size of particles comprising a valve seat having an internal passage, 9. face of said valve seat comprising a valve seat surface, an end of said passage being in said face of said valve seat, a valve having a valve face facing said face of said valve seat, a blade member located in said passage and means for providing relative rotational movement between said blade member and said valve seat.

14. An apparatus according to claim 13, comprising means for imparting to said blade member rotational movement within said passage and with respect to said valve seat.

15. A method of reducing the size of particles comprising forcing a liquid slurry of said particles underpressure against a bed of said particles in a cavity in-the face of a valve to force'said valve away from its seat against a yieldable force yieldingly urging said valve toward its seat, and thence through the valve opening between said valve face and its seat at an angle to the direction of flow of said slurry to said valve and at a substantially higher velocity than the velocity of said slurry to said valve against an impact surface.

16. A method according to claim 15, wherein rotational movement isimparted to said valve and hence to said cavity while said slurry is forced against said bed and through said valve opening and against said impact surface.

17. A method according to claim 15, wherein said liquid slurry is flowed throughta passage in said valve seat against said bed of particles in said cavityand wherein rotational movement is imparted to said valve seat while said slurry is forced against said bed and through said valve opening and against said impact surface.

18. A method according to claim 15, wherein rotary motion is imparted to said impact surface while said slurry is forced against said bed and through said valve opening and against said impact surface.

19. A method according to claim 15, wherein said liquid slurry is flowed through a passage in said valve seat against said bed of particles, said passage containing a blade member and imparting rotary motion to said blade member to agitate the slurry.

20. An apparatus for reducing the size of particles comprising a portion having an internal passage through which a liquid slurry of said particles under pressure is adapted to flow, an end of said passage being in a face of said first portion, a second portion having a face facing said face of said first portion, said faces being adapted to be spaced closely to each other to form a highly restricted opening therebetween extending at an angle to the longitudinal center axis of said passage and having a width which is substantially smaller than the Width of said passage, means for delivering a liquid slurry of said particles to said passage and restricted opening under a high pressure to force the slurry through said restricted opening at an angle to the direction of flow through said passage and at a high increased velocity, a blade memher located within said passage and means for rotating said blade and said first portion with respect to each other.

21. An apparatus for reducing the size of particles comprising a portion having an internal passage through which a liquid slurry of said particles under pressure is adapted to flow, an end of said passage being in a face of said first portion, a second portion having a face facing said face of said first portion, said faces being adapted to be spaced closely to each other to form a highly restricted opening therebetween extending at an angle to the longitudinal center axis of said passage and having a width which is substantially smaller than the width of said passage, means for delivering a liquid slurry of said particles to said passage and restricted opening under a high pressure to force the slurry through said restricted opening at an angle to the direction of flow through said passage and at a high increased velocity, an impact member having an impact surface facing and spaced from the peripheral edges of said faces and extending at an angle to said faces, said impact surface facing the outlet of said restricted opening whereby said slurry discharged from said opening is impacted against said impact surface at high velocity, and means for rotating said impact surface during operation of said apparatus.

References Cited in the file of this patent UNITED STATES PATENTS 251,803 Starkey Jan. 3, 1882 1,363,572 Dalzell Dec. 28, 1920 1,654,268 Nielsen Dec. 27, 1927 1,690,668 China Nov. 6, 1928 1,987,944 Rafton Jan. 15, 1935 2,164,409 Johnson July 4, 1939 2,387,548 Wiegand Oct. 23, 1945 2,672,882 Bergquist Mar. 23, 1954 

